Alkylene oxide may be converted into a cyclic alkylene carbonate in the presence of a suitable catalyst. Such processes have been described for example in U.S. Pat. No. 4,508,927 and Japanese patent application No. 73022702. These patent specifications describe processes in which an alkylene oxide is reacted with carbon dioxide in the presence of a catalyst containing phosphorus to form the cyclic alkylene carbonate. The catalyst can be an organic phosphonium halide as described in U.S. Pat. No. 4,508,927 or an organic trisubstituted phosphine as described in Japanese patent application No. 73022702.
WO-A-03/000641, which is a not-prepublished document, relates in its second aspect to the use of a homogeneous carbonation catalyst in a first carbonation reaction zone and a heterogeneous transesterification catalyst in a second reaction zone for reacting ethylene oxide with carbon dioxide. The carbonation catalysts preferably are alkali metal halides such KI or quaternary ammonium halides.
U.S. Pat. No. 5,847,189 describes processes for hydrolyzing cyclic alkylene carbonates to produce a diol and carbon dioxide. Additionally, U.S. Pat. No. 5,847,189 describes that it is advantageous to convert cyclic alkylene carbonate with an alcohol into alkylene glycol and a dialkylcarbonate.